Sensor Bus; Address; Power - Decagon Devices 5TE Operator's Manual

5TE Operator's Manual
6. Communication

Sensor Bus

There are both positive and negative elements of the SDI-12
protocol. On the positive side, up to 62 sensors can be con-
nected to the same 12 V supply and communication port on
the datalogger. This simplifies wiring because no multi-
plexer is necessary. On the negative side, one sensor prob-
lem can bring down the entire array (through a short circuit,
etc.). To avoid this problem, we recommend the user make
an independent junction box with wire harnesses where all
sensor wires are wired to wire lugs so sensors can be dis-
connected if a problem arises. A single three-wire bundle
can be run from the junction box to the datalogger.

Address

The SDI-12 protocol requires that all sensors have a unique
address. 5TE sensors come from the factory with an SDI-12
address of 0. To add more than one SDI-12 sensor to a sys-
tem, the sensor address must be changed. Address options
include {0...9, A...Z, a...z}. The best and easiest way to
change an address is to use Decagon's ProCheck (if the
option is not available on your ProCheck, please upgrade to
the latest version of firmware). SDI-12 addressing can be
accessed in the "CONFIG" menu by selecting "SDI-12
Address". Addresses may then be changed by simply press-
ing the up or down arrows until you see the desired address
and pushing "Enter".

Power

The sensor can be powered using any voltage from 3.6 to 15
VDC, but 12 V is optimal. Although SDI-12 protocol allows
the sensors to be continuously powered, you may connect
the power (white wire) to a switching source. This can help
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